OSAKA - High concentrations of potentially carcinogenic PFAS “forever chemicals” have been found in Tsushima leopard cats – a designated natural monument and vulnerable species native to a Japanese island – researchers said on July 10.

The Ehime University-led research team found the chemicals in the organs of all 21 cats examined, raising concerns about the impact of pollution on wildlife conservation across Japan.

Used in products such as firefighting foam and nonstick cookware coatings, PFAS are known as forever chemicals because they are highly resistant to breakdown, and accumulate in soil and water as environmental pollutants.

“For the protection of all wild animals, not just the Tsushima leopard cat, there must be a nationwide survey and investigations to identify the pollution source,” said Kei Nomiyama, an associate professor at the university in western Japan.

Tsushima leopard cats inhabit the island of Tsushima in south-western Japan’s Nagasaki Prefecture, and are listed as vulnerable on the Environment Ministry’s Red List of endangered species.

Their numbers have declined due to habitat loss and roadkill. The government estimates that around 100 remain, and zoos in Japan are working to breed the species.

The research team received permission from the ministry to examine the livers and kidneys of 21 dead wildcats that died between 2022 and 2025, testing for 37 PFAS chemicals.

Nearly all the cats had PFAS concentrations exceeding toxicity thresholds in liver cell tests, indicating potential risks to liver function, according to the study. Kidney concentrations were also considered high, it said.

No significant differences based on age, sex or location were recorded.

The median concentration of PFAS chemicals was eight times higher than levels found in a study of European wildcats in Germany.

Experts suspect marine debris and illegal dumping as sources of the pollution, with concentrations likely accumulating through the food chain.

The team also measured persistent organic pollutants, known as POPs, in 19 cats, with some showing extremely high levels of contamination.

Mr Nomiyama said there is a “strong possibility” the pollution is connected to the species’ declining population. KYODO NEWS

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